1. Field of the Invention
The present invention relates to a printed circuit board, and more specifically, to a printed circuit board having a via and a forming method thereof.
2. Description of the Prior Art
Printed circuit boards are necessary components in the electronics industry, which can be applied to electronic products' motherboards for mounting other electronic components and providing wires to be utilized by other electronic components. Alternatively, a printed circuit board can be an adapter of a semi-product and mount the semi-product on a motherboard. Processing steps of a printed circuit board according to a related art include drilling, electroplating, wire etching, pressing, anti-soldering, tin-emitting etc. When a printed circuit board is utilized as an adapter, an application method of it is to drill and electroplate the adapter to form a via which is electrically connected between circuits on the front of the adapter and circuits on the back of the adapter. The front of the adapter is utilized for installing an application circuit, and the back of the adaptor adsorbs solder by using the via, in order for the application circuit to be mounted on the motherboard. In this way, the application circuit on the front of the adapter can be connected to circuit(s) on the motherboard using the via.
Sometimes, for protecting the application circuit from being oxidized or being destroyed by external factors, a method well known in the art is to packet and mold the application circuit. In order to prevent the compound(s) utilized during the molding process from flowing through the via to the back of the printed circuit board, it is necessary to manually seal a terminal of the via on the front of the printed circuit board with insulating stickers. Furthermore, when mounting the adapter on the motherboard, an insulating sticker can prevent the solder from flowing from the back of the printed circuit board to the front of the printed circuit board, so the application circuit will not short circuit. However, when the size of the via becomes very small, it is difficult to perform the above-mentioned operations manually. A method according to another related art is to fill a terminal of the via on the front of the printed circuit board with a blocking material, such as a solder mask, and at the same time, keep a terminal of the via on the back of the printed circuit board not filled, to adsorb the solder. However, the present method still has some limitations; for example, when the diameter of the via is too small, the terminal of the via on the back of the printed circuit board may not adsorb sufficient solder; when the diameter of the via is too large, the blocking material may sink causing the front of the printed circuit board to not be smooth, and furthermore, the filled blocking material may not bear the force from the molding process, causing the via to break and the compound to flow.